Mikel Arteta vented his fury with Arsenal's performance and VAR after the Gunners fell to a dismal 1-0 defeat by Everton.
Bernd Leno committed a costly error by letting Richarlison's effort through his legs to set the Toffees on course to return to Merseyside with all three points.
Earlier in the second half, Richarlison conceded a penalty for a foul on Dani Ceballos, but VAR intervened to determine Nicolas Pepe was offside in the build-up by the slightest of margins.
The result marks Arsenal's seventh home defeat in the Premier League this season, which is the most they have suffered since the 1992/93 campaign.
Arteta was clearly exasperated as he assessed the match, labelling his side's performance "unacceptable" and demanding answers over the controversial VAR decision.
"We were the better team but there are certain decisions that we can't control," he told Sky Sports .
"To disallow a penalty 15 seconds before - [we had] eight or nine touches [after Pepe was offside] - I saw it 10 times and I don't get it.
"It can be taken the way they want. Zero control. Somebody has to explain that.
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"We were the better team. We lacked some clear-cut chances and the edge in the final third.
"They are very well organised but we conceded the goal in the wrong moment and when we had the penalty but it wasn't given."
Arteta also admitted the result was "damaging" for Arsenal's confidence ahead of their Europa League semi-final with Villarreal on Thursday.
He added: "Errors are part of football, we conceded an own goal that defined the game at the end. We didn't create enough against a team that is well organised, we lacked clarity in the final third.
"We need to go through the disappointment and focus our energy, the semi-final is more than crucial for us. I don't want to use any excuses, I understand the protests."
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